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 Post subject: How to read old lenses?
PostPosted: Wed Apr 16, 2008 4:04 pm 
I am looking to get some older OM manual focus lenses but needed some help reading them...
There is one that has this on it :
Olympus OM-SYSTEM ZUIKO AUTO ZOOM 100-200mm 1:5 Lens

Is that 100-200mm f5 ? and will that"convert" to a 150-300 with the digital sensor .... i always see that the lens is "equivilant to xxx in film"

as a side note... how well do they work ? I have an olympus e-510 and am purchasing the 4/3s to om converter from olympus.

Thanx in advance....


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 Post subject:
PostPosted: Wed Apr 16, 2008 4:28 pm 
Hi TheHawk1973,

your first thought is correct: 100-200 mm/f5. Because of the "cropfactor" the lens has a different focal length on our DSLR.
Nikon has a factor of 1.5, Canon of 1.6 and Olympus 2(???).
I don´t know for sure. If the latter where true, you have a 200-400 mm lens. If it´s gonna work on a new body must be answered by someone who has an Oly, I can´t :oops:

Kind regards,

ngc94227


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 Post subject:
PostPosted: Wed Apr 16, 2008 4:54 pm 
Just so im clear .....

This lens :
NEW 135mm F2.8 MULTI COATED AUTOMATIC TELEPHOTO LENS FOR THE OLYMPUS OM

Would be a 200 to 270mm(aprox) with a f2.8?

and the 100-200mm f5 would convert to a 170-340(aprox) with a f stop of 5?

or am i confused :roll:


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 Post subject:
PostPosted: Wed Apr 16, 2008 5:47 pm 
I googled somewhat on cropfactor, and indeed your camera has a cropfactor of 2. That means that a lens of 135 mm focal length is 270 mm (2 x 135mm) on yours, comparing it to the "old" SLR with 24x36 mm filmformat, or DSLR´s with fullframe sensors. And your 100-200 mm will be 200-400 mm.
In the past, a lens of 50 mm focal length could be compared to how the human eye would "see" it. From that follows that your camera would need a 25 mm focal length to obtain those 50 mm. Lenses above these 50 mm are telelenses, around 50 normal and beneath 50 are wideangles.

But if these lenses can be used on your camera should be pointed out by somebody else, because I can´t say. But when yes, it can mean that eg. autofocus doesn´t work. Again, I´m a Nikonian and can´t speak for Oly.
EDIT: I saw that you already mentioned yourself that these lenses are with manual focus.....
ngc94227

P.S. your lenses 14-42 will be 28-84 mm. and the 40-150 will be 80-300mm. That means that you have all focal lengths from 28-300mm.
So you have everything, but not a wideangle yet (if you need it, though)


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 Post subject:
PostPosted: Wed Apr 16, 2008 5:59 pm 
Quote:
your lenses 14-42 will be 28-84 mm. and the 40-150 will be 80-300mm. That means that you have all focal lengths from 28-300mm.
So you have everything, but not a wideangle yet (if you need it, though)


So... my 40-150 is equlivilant to a 80-300mm ......

but if i put a "film camera lens" that is 100-200 mm on my DSLR it will give a focal length of 200-400mm ?

I just want to knowas i was looking for a FAST lens but in the 40-80mm range...so that means the older lens would need to be 20-40mm .... right ?!??! :roll:


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 Post subject:
PostPosted: Wed Apr 16, 2008 6:22 pm 
Everything correct, but the word "fast" means something else.

focal length is for magnifying so to speak. A lens with 300 mm focal length magnifies 6x (300/50) comparing to a 50 mm lens. This is why telelenses (focal length > 50 mm) magnifies and wideangles (FL<50) the field of view will be greater. The telelens narrows your field and a wideangle increases it (that´s why they are called so).

"fast" means a low f-number. How lower the f-number, more light is captured on film or sensor. So you can shoot foto´s where it is somewhat darker (backlit situations) easier. If you have two lenses with SAME focal length but the first is F/2 and the other F5.6 then you can take pictures in cases of backlighting where the second would fail to give a good result.

If you have more question please let know.
ngc94227


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 Post subject:
PostPosted: Thu Apr 17, 2008 5:09 am 
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Joined: Tue Nov 08, 2005 3:32 pm
Posts: 9975
Location: Queenstown, New Zealand
PS - don't forget we have a guide to lenses and lens terminology here:

http://www.cameralabs.com/lens_guide/Le ... uide.shtml


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